A radio access system and the evolution of a radio network, of cellular mobile communication (hereinafter, also referred to as “long term evolution (LTE)” or “evolved universal terrestrial radio access (EUTRA)”), and a radio access system and a radio network that utilize a frequency band wider than that of LTE to realize faster data communication (hereinafter, also referred to as “long term evolution-advanced (LTE-A)” or “advanced evolved universal terrestrial radio access (A-EUTRA)”) have been conventionally studied in 3rd generation partnership project (3GPP).
As communication systems in LTE, an OFDMA (Orthogonal Frequency Division Multiple Access) system performing user multiplexing by using subcarriers orthogonal to each other, and an SC-FDMA (Single Carrier-Frequency Division Multiple Access) system have been studied. That is, in a downlink, the OFDMA system that is a multi-carrier communication system has been proposed, and in an uplink, the SC-FDMA system that is a single-carrier communication system has been proposed.
In contrast, as communication systems in LTE-A, in a downlink, it has been studied to introduce the OFDMA system, and in an uplink, it has been studied to introduce a clustered-SC-FDMA (also referred to as Clustered-Single Carrier-Frequency Division Multiple Access, DFT-S-OFDM with Spectrum Division Control, or DFT-precoded OFDM) system in addition to the SC-FDMA. Here, in LTE and LTE-A, the SC-FDMA system and the clustered-SC-FDMA system proposed as uplink communication systems have characteristics that can suppress PAPR (Peak to Average Power Ratio, or transmission power) during data (information) transmission to be low due to the characteristics of the single-carrier communication system (due to single-carrier characteristics).
Furthermore, frequency bands used in ordinary wireless communication systems are contiguous in LTE-A, whereas it has been proposed that a plurality of contiguous and/or discontiguous frequency bands (hereinafter, also referred to as component carriers (CCs) or carrier components (CCs)) is compositely used, and thus, is operated as one wide frequency band (also referred to as a carrier aggregation). Furthermore, it has also been proposed that a frequency band used in downlink transmission and a frequency band used in uplink transmission have different frequency bandwidths (an asymmetric carrier aggregation) so that a base station apparatus and a mobile station apparatus (UE: User Equipment) use more flexibly a wide frequency band to perform communications (Non-patent document 1).
FIG. 6 is a view illustrating a carrier-aggregated wireless communication system in the conventional art. It is also referred to as symmetric carrier aggregation that a frequency band used in downlink (DL) communication and a frequency band used in uplink (UL) communication as shown in FIG. 6 have the same frequency bandwidth. As shown in FIG. 6 a base station apparatus and a mobile station apparatus can perform communication in a wide frequency band configured by a plurality of component carriers by compositely using the plurality of component carriers that is contiguous and/or discontiguous frequency bands.
FIG. 6 shows that as an example, a frequency band (or DL system band (DL system bandwidth)) used in downlink transmission that has a bandwidth of 100 MHz is configured by five downlink component carriers (DCC1: Downlink Component Carrier 1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz. Furthermore, as an example, FIG. 6 shows that a frequency band (or UL system band (UL system bandwidth)) used in uplink transmission that has a bandwidth of 100 MHz is configured by five uplink component carriers (UCC1: Uplink Component Carrier 1, UCC2, UCC3, UCC4, and UCC5) each having a bandwidth of 20 MHz.
In FIG. 6, downlink channels such as a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) are assigned in respective downlink component carriers.
The base station apparatus allocates (schedules) downlink control information (DCI) for transmitting a downlink transport block transmitted by using a PDSCH to the mobile station apparatus by using a PDCCH. The base station apparatus transmits a downlink transport block to the mobile station apparatus by using a PDSCH. Here, in FIG. 6, the base station apparatus can transmit, to the mobile station apparatus, up to five downlink transport blocks (or PDSCHs) at maximum in the same subframe.
Furthermore, uplink channels such as a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH) are assigned in respective uplink component carriers.
The mobile station apparatus transmits, to the base station apparatus, uplink control information (UCI) such as channel state information (CSI) indicating a downlink channel state, information indicating an ACK/NACK (Positive Acknowledgement/Negative Acknowledgement) in HARQ for a downlink transport block, and a scheduling request (SR) by using a PUCCH and/or a PUSCH. Here, in FIG. 6, the mobile station apparatus can transmit, to the base station apparatus, up to five uplink transport blocks (or PUSCHs) at maximum in the same subframe.
Similarly, FIG. 7 is a view illustrating an asymmetrically carrier-aggregated wireless communication system in the conventional art. As shown in FIG. 7, the base station apparatus and the mobile station apparatus can perform communication in a wide frequency band: by causing a frequency band used in downlink transmission and a frequency band used in uplink transmission to have different frequency bandwidths; and by compositely using component carriers that are contiguous and/or discontiguous frequency bands constituting these frequency bands.
FIG. 7 shows that as an example, a frequency band having a bandwidth of 100 MHz and used in downlink transmission is configured by five downlink component carriers (DCC1, DCC2, DCC3, DCC4, and DCC5) each having a bandwidth of 20 MHz. Furthermore, as an example, FIG. 7 shows that a frequency band having a bandwidth of 40 MHz and used in uplink transmission is configured by two uplink component carriers (UCC1 and UCC2) each having a bandwidth of 20 MHz.
In FIG. 7, downlink/uplink channels are assigned in respective downlink/uplink component carriers. The base station apparatus allocates (schedules) a PDSCH to the mobile station apparatus by using a PDCCH, and transmits a downlink transport block to the mobile station apparatus by using the PDSCH. Here, in FIG. 7, the base station apparatus can transmit, to the mobile station apparatus, up to five downlink transport blocks (or PDSCHs) at maximum in the same subframe.
Furthermore, the mobile station apparatus transmits, to the base station apparatus, uplink control information such as channel state information, information indicating an ACK/NACK in HARQ for a downlink transport block, and a scheduling request by using a PUCCH and/or a PUSCH. Here, in FIG. 7, the mobile station apparatus can transmit, to the base station apparatus, up to two uplink transport blocks (or PUSCHs) at maximum in the same subframe.
In LTE-A, a sounding reference signal (A-SRS: Aperiodic Sounding Reference Signal) transmitted only when a transmission request is notified by a PDCCH from the base station apparatus has been proposed. By including A-SRS transmission indication information (A-SRS activation/deactivation) in a downlink control information (DCI) format (also referred to as a DCI format), the mobile station apparatus can determine whether or not the base station apparatus requests transmission of an A-SRS, and can dynamically perform transmission control of an A-SRS. Furthermore, it has been proposed that the base station apparatus: indicates the mobile station apparatus to perform transmission of an A-SRS, by using a downlink control information format (also referred to as a DCI format, a downlink grant, or a downlink assignment) for a downlink; and indicates the mobile station apparatus to perform transmission of an A-SRS, by using a downlink control information format (also referred to as a DCI format, an UL grant, or an uplink assignment) for an uplink. Furthermore, it has been proposed to indicate an indication of transmission of an A-SRS by one bit (or multiple bits) of an uplink grant or a downlink assignment, or a predetermined code point (Non-patent document 2).